1. Field of the Invention
The present invention generally relates to a method and a device for luminance correction and, more particularly, to a method and a device for luminance correction to efficiently adjust luminance and enhance the contrast between each color of digital images.
2. Description of the Prior Art
With the arrival of the digital era, the digital video replaces the traditional analog video gradually. Owing to the popularity of digital video, digital image processing is being paid attention to.
Taking photography of digital cameras forming digital images for example, the sensing device of digital camera for detecting incoming light while taking picture is made of CCDs (charge-coupled device) in array arrangement. Each CCD has a color filter (red, green or blue). Therefore, each CCD can sense the intensity of a monochromatic light (R, G, or B) through its filter while light projects on the CCDs.
Accordingly, the process of taking pictures by the digital camera to produce digital images, at first, enables the light into camera lenses, senses the light and generates corresponding induced current, representing the R, G, or B value of a pixel, through the CCDs of the digital camera. The image processing unit of the digital camera generates the digital image utilizing the R, G, and B values of pixels. The colors of each pixel are seen as variable combinations of the so-called primary colors red (R), green (G), and blue (B).
In order to adjust the images shown on a display monitor, like a TV, a conventional method for luminance correction is to find out the corresponding luminance signal (Y) and chrominance signal (C) according to the R, G, and B values of pixels in an image. Luminance correction according to the prior art adjusts the luminance signal directly. In other words, the prior art directly adjusts the corresponding luminance signal of the digital image for luminance correction.
In the prior art method, although the luminance of a digital image can be adjusted, the luminance of each pixel is adjusted with the same gain value at the same time. Therefore, the degree of luminance correction for each pixel is identical. In other words, the contrast between each color in the digital image becomes lowered using the conventional method for luminance correction.
Therefore, there is need in providing a method and a device for luminance correction to prevent the contrast between each color from becoming lowered while adjusting the luminance of digital image. Furthermore, the present invention provides high luminance and improves the contrast between each color in the digital image while adjusting the luminance of digital images.